The invention relates to a device for the treatment of or for action on workpiece surfaces by means of an actuator, such as a laser for cutting or engraving, a nozzle for applying oils, varnishes, adhesives, paints, etchants, releasing agents, etc. The invention in particular relates to a device which is suitable for working on workpieces with relatively large surfaces—in relation to the dimensions of the actuator—such as on belt materials.
Systems are known from the prior art that allow the working range of an actuator to accurately adjust in the x-, y-, and z-direction relative to the workpiece surface. Cross beams, for example, which are coupled with length measurement devices are used for the adjustment of an actuator in the x-y direction. Such systems are hereinafter referred to as linear drives.
Depending on the process of surface treatment or on the effect of a treatment on the surface, different high accuracies in the positioning of the actuator are required.
Various constructions are known for the positioning of an actuator with respect to a workpiece surface. It is especially known from the prior art to position the actuator with the technologically required accuracy and to guide it over the workpiece surface in order to process it by means of sensors which measure lengths and distances. Certain conditions must therefore be complied with, such as the positioning accuracy, the controllability, the weight of the actuator, the volume of construction or the lowest possible production cost of construction used for the positioning of the actuator.
Basically, it is required that the positioning system does not influence the processing process to be carried out by the actuator, i.e., does not interfere. If the distance of an actuator to the workpiece surface is to be monitored, that can be done with a tactile operating measuring system which has a wheel at its front end that rolls on the workpiece surface. However, mechanical scanning is possible only for a relatively solid surface. Distance sensors which scan the workpiece surface without contact are used with touch-sensitive surfaces, such as capacitive and inductive distance sensors or even dynamic pressure nozzles that operate pneumatically. However, these sensors can interfere with the processing process or can be disturbed by the processing process. Thus, the gas emerging from the dynamic pressure nozzle, usually compressed air, generates turbulence in the vicinity of a paint spray nozzle. Such interference may also occur in the application of etchants, varnishes or low-viscosity adhesives. Thus, the air flow of a dynamic pressure nozzle could also swirl the protective gas during gas-shielded welding.
Furthermore, it should be noted that the solid, liquid or gaseous substances released by the actuator or even substances arising from the treatment of the workpiece surface can influence the measurement accuracy of the distance sensors. When process fluids reach into the range of, for example, measuring electrodes, the distance measuring signals are distorted.
These problems can then be remedied if the measuring system for measuring the distance between the actuator and the material surface is spatially separated from the actuator. However, a measuring system arranged far away from the actuator generates greater measurement error than a measuring system arranged directly on the actuator. In addition, increased device-related effort is necessary in order to reduce the measurement error.
Devices and methods are described in the documents DE 10059232 C2, DE 19938328 C2, DE 102010027031 A1 and DE 102007047298 B3 that position a work unit at a predetermined distance above a workpiece surface by means of a sensor arrangement.